Color television system



July 8, l947- A. N. GoLDsMm-l 2,423,759

COLOR TELEVISION SYSTEM Filed Aug. 2.1, 1942 2 sheets-sheet 1 July 8,` 1947.

A. N. GVOLDSMITH COLOR TELEVISION SYSTEM Filed Aug. 2'1, 1942 2 Sheets-Sheet 2 Smm ' Patented July 8, 1947 COLOR TELEVISION SYSTEM Aurea N. cammina" rm, N. Y.. mimmto Radio Corporation of America, New York,

N. Y., a corporation oi' Delaware Application August 2,1, 1942, Serial No. 455,553

This invention relates to color television systems, and methods, and more particularly, to a color television method and system in which there is provided a key image to augment and improve the color rendition andl brilliancy of the finally reproduced television image.

In a color television system, it is usual to employ 4three primary color component images superimposed either cyclically or simultaneously to reproduce a color image having the same colors as the object of which the image is a representation. Two-component color television systems are also known, but `su'er from relatively inferior iidelity of color reproduction and, thus, color television d"systems usually employ the three-color process.

While it is theoretically possible to achieve nearly perfect color reproduction under idealized conditions by the three primary color component method, there is, actually, considerable diver- "gence from such ideal conditions in practice, due to the i'act that the analyzing filters, the spectral sensitivity of the light sensitive medium, and the spectral response characteristics of the reproducing medium, do not have the required characteristics necessary to meet the theoretical requirements for reproduction. For example. it is well known in the theory of three color reproduction that three properly chosen pure spectral colors are suiiicient to reproduce substantially all of the colors lying within the trichromatic color triangle. However, light sensitive mediums have an irregular spectral response, and color reproducing mediums are far from pure spectral colors.v

The color iilters required for analyzing the colors'` of the object likewise do not have sharp cutoifs with a band of uniform transmission, but have sloping cutois and non-uniform transmissions through the passbands. This departure from ideal conditions, therefore, tends to degrade the quality of the color reproduction.

By my invention, in which I add to the three primary color component images a neutral black and white image, I improve the color reproduction of television images by increasing the brilliancy of the highlights, and increasing the density in the shadow areas.

Moreover, by my invention in which the pr mary color component images are controlled in accordance with a black and white image, I also provide correction for the overlapping of lters and the departure of ideal spectral response oi the reproducing medium, so as to provide purerv colors with greater saturation, and with more iidelity with respect to the original colors.

2Q Claims. (Cl. P18-5.2)

In accordance with my invention, I provide a method and apparatus for producing a key image of substantially neutral tint which is added to the three primary color component images, and, in addition, regulate the color component images vwith regard to intensity under the control of the key image brightness at corresponding elemental areas. By such a method, the `departure trom ideal characteristics of the analyzing iilters, the light sensitive characteristic of the transmitting medium, and the spectral response of the light emitted from the reproducing medium `are in some measure compensated, so that essentially the distortions arising from the imperfections of the actual elements used are in part eliminated.

Moreover., the signals which are to be transmitted as representative of the key image may be derived from the inirared, the visible, or the ultra-violet portions of the spectrum of the light reected from the object. Alternatively. the key image may be produced from one or more of the color components scanned in any predetermined order and used to control the primary color images in any desired proportion.

The key image, moreover, may be derived by utilizing an orthochromatic image projected upon the light sensitivesuriace of the transmitting tube, or by direct projection of the image of the object upon the mosaic of a suitably color-sensitive transmitting tube without theinterpositionv ing oi' a illter. Where cyclic transmission of the color component images is utilized, suitable delay circuits may be interposed so that the signal resulting from the key image scanning may in proper proportion be appropriately added to, or subtracted from, the image corresponding to the color component being scanned.

Accordingly, it is an object of my invention to provide an improved method of transmitting color television Images.

Another object of my invention is to provide apparatus for improving the fidelity of color television images.,

Still a further object of my invention is that of improving the detail, resolution and delineation of color television images by adding to the realism and naturalness of the color reproduction and, as well, by increasing the contrast and gra# dation ranges in color reproduction.

Yet another object of my invention is to provide the addition of a key image to color component images in additive or subtractive color television systems in which the color component images are either simultaneously scanned or cyclically scanned.

' Again, it is an object of my invention to provide ay key image or substantially neutral tint to be added to each group oi color component pictures in a color television system.

A further object oi my invention is the production of key images and the use o! a color lter, which in conjunction with the chromatic photosensitivity of the mosaicproduces an orthochromatic rendition of the image, that is to say, a rendition in which brightness values correspond to the apparent brightness as viewed by the normal eye, of the various colors in the scanned image iield or raster.

Yet again, an object of my invention is the production of a key printer image by usinga suitable filter, which, in conjunction withfthe chromatic photosensitivity of the mosaic o! the transmitting tube, shall be predominantly responsive in the infra-red, in the visible, or in the ultra-violet portion of the spectrum.

A still further object of my invention is the electrical control of the brightness of each color component image in accordance with the key image values at the corresponding portion of the image, whereby the brightness of the color component images is suitably reduced so that the addition ofthe key* image brightness provides a final combined -color picture of correct brightness.

Another object of my invention is to provide a color television systemv in which key images are produced by the equalized transmission and reception of each of the tri-color component images.

Other objects of my invention will becomerapparent to those skilled in the art upon a reading of the following detailed description, taken in conjunction with the drawing.

In the drawing, there is shown at Fig. 1 a schematic representation of a filter disc for use in a sequential type of scanning color television system, in which there is provided an orthochromatic sector as well as a red, green Vand blue Fig. 2 shows in schematic form an appropriate receiver disc having a blank sector portion in addition to the red, green and blue portions:

Fig. 3 shows in block diagram form, circuit connections of ,apparatus for providing the key image signal and for controlling the primary color component image signals in accordance with my invention; and,

Fig. 4 is a schematic representation ot a further modiflcation of the system wherein the several component color images are simultaneously transmitted for simultaneous reproduction at receiving points and an equalizedA or key4 image corresponding tothe orthochromatic image, and thus the intrinsic brilliance of the several colored images, is transmitted in a cyclic manner.

Fig. 1 shows a four-sector rotary iilter disc intended to rotate'before the mosaic of a suitable camera or image scanning tube at such a -rate that one of the color. sectors is in front o! the mosaic substantially throughout the time of the scanning of the corresponding color component picture. The disc i is provided with four sectors, and, as an example, sector 3 may be a red filter, sector 5 a green illter, sector 1 a blue "illter, while sector 9 may be an orthochromatic liilter. Alternatively, of course, it will be un- A 4 illter describes the'color of the light which is transmitted by th'e illter.

Moreover, it will be appreciated that alternatively the orthochromatic filter 9 may be removed and thesector occupied by this filter left blankto provide the signal for the black and white key image.

Fig. 2 shows a corresponding filter disc to be used at the receiver in register with the image reproduction. 'I'he disc Il is provided with the red, green and blue lters, I3, I5 and l1 respectively, and a blank sector I9. The red, green and blue color component images are reproduced on the screen by the introduction of the corresponding filter sectors ;l3, |5 and l1, in appropriate time relation, into the optical system, whereby the individual images are viewed or projected or otherwise observed. The key image is produced and viewed throughv the clear or blank sector I9' of the disc Il. The

'black and white image produced during this peboth the key image and the three color compo- In Fig. 3, the image of the object 2 nent images. to be transmitted is thrown by the opticalsystem 2| upon the mosaic electrode 3| of an image scanning or camera tube 21. The camera'. or image scanning tube 21 may be of the general type known as the "Iconoscope and described by Zworykin and others, or the scanning tube may be of the type known in the art as the image` Iconoscope or the Orthicon, or it may be one of the type known as the image dissector, all o! which have been disclosed both directly and by footnote reference in the book Principles of- Television Engineering by D. G. Fink and published in 1940 by McGraw-Hill Book Co. For convenience, reference herein will be made to a scanning tube of the Iconoscope type as illustrative of the principles of operation. The

image, in traveling to the mosaic electrode 3l, passes through the lter disc 25, the disc being of the form shown in Fig. 1, and driven by a motor 23. An electron gun 35 produces an electron beam which scans the mosaic 3l to provide, through the means of released electrons, the video signal, which signal is carried by the signal plate 29 to the video amplifier 39 as is well understood in the art. The deilection coils 31 serve to produce 4the bi-directional scanning action of the beam of electrons released from the gun 35, and the released electrons are collected by the collector electrode 33. as is also well known in the art. Deflection of the electron beam is provided by suitably energizing the deilecting coils 31 under the control o! energy of predetermined wave form and frequency, as is known in the art.

A commutator device 40 is' mechanically coupled to and driven in synchronismwith the motor 23. The commutator 40 is provided withrfour segments 43, 45, 41 and 49, each of the segments being connected to a collector ring, respectivelyV numbered 5|, 53, 55 and 51. A brush Il bears 4on the commutator segments and serves to fur- ,nishthe video signals from the ampliiier 39 to each of the collector rings in sequence. 'I'he video signals fed to the collector rings are led to ananas signals generated by the camera or image scanning tube 21, when the orthochromatic illter 9 is in such angular position in its rotation as to be in register with the mosaic electrode 3| of the scanning tube. The brush 6| is active to supply signals to the ampliiler 81 when the red filter sector 3 is in register with the mosaic of the scanning tube 21, while the brushes 63 and 65 similarly feed energy to the ampliiiers 99 and 9| respectively, when the green and the blue iilters are in register with the mosaic element of the scanning tube 21.

The signals representative of the orthochromatic image are fed through the orthochromatic image signal amplifier 61 and through the lead 69 to the combining amplifierunit 93, the ampliiler unit 61 serving to regulate the intensity of the video signals to be transmitted representative of the orthochromatic image. A portion of the output energy from the amplifier unit 61 is fed to each'oi' the delay networks 69, 1| and 13, which are conventionally represented. Y

Delay networks are, per se. well knwn in the art and generally comprise series inductance elements and. shunt capacity elements with a suitable terminating resistance. Thus, for simplicity of disclosure, the delay networks are merely shown in schematic form, and it is to be understood that such delay circluts may, in many instances, assume the status of an artificial line with the delay characteristics a function of the delay time required.

The delay network 69 introduces a delay time of the video signals corresponding to the orthochromatic image equal to the time required to scan one picture iield, while the delaynetworks 1| and 13 introduce a time delay equivalent to two field scannings and three field scannings respectively. The output of the delay networks 69, 1| and 13 are fed to reversing switch units 15, 11

and 19 respectively, and thence to the conventionally indicated volume controls 8|, 93 and 95. which are preferably in the form of potentiometers. Each of the volume controls above named thenI supplies energy to the mixer and gain control amplier units 95, 91 vand 99 respectively, and the outputs of these three units are then combined with the signal corresponding to the signals simultaneously in a cyclic system.

In the operation of the system, the series of signals corresponding to the orthochromatic image are transmitted to the combining-unit 93 through the conductor 69, without time delay, after amplification in the ampliiier unit 61. At the completion of the scanning of the orthochromatic image, the disc I is turned, for instance, to such a position that the red lter 3 is intermediate the optical system 2| and the mosaic element 3| of the scanning tube 21. In this way, by means of the commutator 40 providing the desired and proper sequencel of switchingfthe signals corresponding at the red image are then supplied by way of the brush contact 6| to the red image signal amplifier unit 91 whose output 'is fed to the mixer 6 amplifier 95, and from it to the combining unit 93 and thence to a transmission channel of any desired type and description, which has not been shown specifically. At the same time that the signals are developed from the vcamera or image scanningytube 21 in accordance with the light revealed to the mosaic through .the red illter 9, the signals of the orthochromatic image, as they appear in the output of the signal amplifier control unit 61, have been passed via the conductor 10 through the delay network 69 and into the reversing switch unit 15 and then through the volume control 9| to control also the mixer ampliiier and gain control unit 95. TheJreversing switch arrangement is provided by any convenient sort of elecl tronic arrangement and is for the purpose of x determining whether or not the series of output signals representing the orthochromatic image shall tend to increase the gain in output of the mixer amplifier and gain control unit 95 or shall tend to reduce the gain. Accordingly, it being assumed that the output signals from the amy'pliiier control unit 61 representing the orthogain control unit-95, it is apparent that a potenchromatic image are delayed one eld scanning period in the delay network 69, it isvapparent that the arrival in the mixer amplifier of the signals from the reversing switch arrangement 15 will coincide substantially in time with the initial scanning of the red image through the lter 3.

Consequently, under conditions when it is de.. sired that provision shall be made for decreasing the gain in the mixer amplier and gain control unit 95 with increases in signal output from the delay circuit for highlights in the scanned subject, a switch element |0| may be placed against the u'pper contact point indicated, so that the output signals from the delay network 59, as conventionally indicated, may pass through a single ampliiler tube |02 and thence through the switch armature to the potentiometer volume control unit 8| and, by virtue of the current owing through the tube |02, increasing with a posi.. tive signal on the control electrode thereof, as will be the tendency for the current flowing through the mixer amplier and gain control tube |05 contained in the mixer ampliiier and tial drop will take place through the potentiometer 9| in such a manner that the variable contact |06 may be set so that the signals impressed upon the control electrode |01 of the tube |05 are negative in polarity when the controlling signals upon a second grid |09 of this same tube, as they are derived in conductor |09 from the amplifier 91, are positive in sign. In this way, the orthochromatic image signals may cause a reduction in the output of the mixer and gain control tube |05 of the amplier unit 95. However, under circumstances where it is desired that the orthochromatic video signals shall increase the gain in the mixer amplifier and gain control unit 95, it is apparent that the switch armature |0| may be moved to its lowermost contact so that the signal output from the tube |02 is now fed through the reversing tube ||0 to provide under the control of the orthochromatic image a reverse polarity of signals on the control electrode |01 of the amplier tube |05 of the mixer amplifier 95. In this Way, depending upon the position of the switch armature |0|, the gain in the amplier |05 may be increased or decreased under the influence of the orthochromatic signals, so that the tube |05, as it serves the mixer amplifier and gain control tube for the red signals, will have 'its output energy controlled not only by the actual signals produced as output energy from the scanning tube mosaic. (and previously ampliiied in amplliler 31) but also will be indirectly controlled by the previously scanned orthochromatic image.

Reference now may be made to the green image signal which is derived through the green filter section of Fig. 1, for instance, and ampliiied in the green image signal ampliiicr I3. A control signal for controlling this signal output has been previously fed from the orthochromatic image signal ampliiier 61 by way of the conductor 1 1l to the delay circuit 1|, wherein it is delayed a predetermined time period (in this example assumed as the period of two image or picture ilelds) and then impressed upon the reversing switch unit 11, the output energy from which controls the Accordingly, the energy 'output from the reversing Y numbers with primes added represent corresponding parts in each ligure. The same will be true of the reversing switch unit 19 and the mixer amplifier 39, hereinafter to be described, except that like parts are designated by like numbers with double primes added.

Accordingly, by properly positioning the switch armature Ill', the potential applied to the control electrode |01' of the mixer |05' may be made of like polarity, oropposite polarity to the signal simultaneously impressed upon the second control grid III', as this last named signal is de, rived from the image signal ampliiier 89, since.

"highlights" are generally related and occur at the same time in the orthochromatic or key image and in each of the images of the primary image colors. Accordingly, depending upon whether or not the reversing switch is in its upper or lower position will determine whether the signal out-,- put is decreased or increased, as was above explained in connection with the signals representing the red images. Likewise, with regard to the blue signals, the output of the orthochromatic image signal amplifier 61 is supplied to the delay circuit, conventionally represented at 13, and -this delay circuit, in contrast to the delay circuits i9 and 1I, so provides that the time delay between the arrival of the signal at the input and the arrival of the signal at the output from' where it is supplied to the reversing switch unit 19 will be a time period coinciding with three picture elds, that is, for instance, the time required to scan all of the orthochromatic, the red and the green images, for instance. Qtherwise,

the arrangement of the blue signal channel substantially coincides with that of the red and the green, hereinabove explained, and, accordingly, the output signal level of the mixer ampliiier'll is determined by the signals applied to each oi' the controlling electrodeslll" andy Il", of which the former potential is controlled by the position of the switch armature lill" in the reversing switch unit 19, and in .which the potential of the latter control electrode is determined by the output of the blue image signal ampliner 0| as supplied to the mixer ampliner l1 by way of the conductor III.

The output energy from the mixer amplifier Il is fed by way ot a conductor III to the combining amplier unit 93. The output from the mixer amplifier al is fed by way of a conductor |.I1 to the s ame combining unit and the output from the mixer ampliner 99 is fed by a similar con. ductor H9 to the same combining unit.

From what hasbeen indicated above, it is'ap'- parent that the sequence oi' energization of the combining ampliiier unit 93, herein represented only schematically since all of the signals may be applied through a common ampliiier channel, will iirst amplify the orthochromatic signals; next the red image signals; next the green-image signals, and lastly the blue image signals, whereupon the cycle will be repeated. Thus, the sequence of transmission, as hereinabove explained, is cyclic, with it being understood that the orthochromatic image may, for the reasons above outlined in the statement of the invention and in some ofthe objects thereof, serve to control the signal output representing the various component vcolor images. Output energy from the combining amplifier unit may then be supplied to .a transmission channel (not shown) via the connecting link |2l. 'I'he transmission channel may be of either the radio transmission link or wire line transmission link where desired. Further, where it is desired, the output from the combining amplier unit 93 may be fed through a second conductor |23 to a monitor |25, at which the'transmission characteristics may be observed.

The monitor arrangement, herein represented only in schematic form, may comprise substantially the arrangement of the usual receiver instrumentality, and thus the signal output from the combining amplier unit 83, as it appears in the conductor |23, may serve, through appropriate controls, to modulate the intensity of an electron beam developed within a cathode ray image reproducing tube for instance. Such an image reproducing tube (not shown) is preferably one of the type wherein `the luminescent screen or'target area upon which the image appears is of such composition as to produce substantially a black and white image, and this image, whenyiewed through the rotary iilter, such as that shown by Fig. 2 for instance, will provide the desired color image reproduction.

From what has been set forth, it is apparent that certain conclusionscan be reached in connection with the positioning of the switch armature ||l| of the various reversing switch units 1 11 and 19 to such a position that the orthochromatic or key image tends to. decrease the output energy from the various mixer ampliiiers 95, 91 and 99 at the corresponding picture point, it being assumed, of course, that synchronous and cophaseal scanning relationships are attained for all of the images representing the various component primary colors, as well as the orthochromatic or key image. l

l'hese conclusions are that in the image which is monitored or the image received at various receiving points, increased definition will be obtained because of the high delineatory capabilities ot the ordinary black and white Vimage reproduction, resultingpf course, from the transmission of the orthochromatic or key image signals in the proper sequence, in which registration problems are not material.

Next, it will be apparent that increased grada... tionranges are obtainable in the observed received image because, in eilect, the highlight brightness is increased by the use of the key image and the shadows are darkened in the component color images by the control action of the key image in the transmitter. f'

Lastly, it is possible to obtain, for substantiallyall conditions of operation. a predetermined maximum level of brightness which will not be exceeded by virtue of the action of the key image signal series controlling the output energy for the individual component color images. It thus becomes apparent that, under no circumstances. will the image receiver or reproducing tube be overloaded, and therefore a greater eiliclency in image reproduction is achieved.

For reasons of simplicity, the disclosure hereinabove made does not provide or disclose arrangements whereby synchronization is established either between the scanning beam action in the scanning tube 21 and a corresponding image reproducing tube of`either the monitor |25 or a receiver (not shown), nor does the disclosure hereinabove provide for arrangements whereby the illter disc I of the transmitter may be synchronous in its operation with theillter disc of the monitor or the receiver. Itis, however, to be understood that in either instance the discs may be driven by suitable synchronous motors, for instance, operating from the same power supply and the scanning beams may be controlled or deected according to well known television technique through the generation and transmission of suitable synchronizing signals caused to follow in sequence each field of transmission and each line of signal energy transmission in each field. For simplicity of illustration, these features are not illustrated. although it is to be understood that such may be and should be added to what has herein been set forth. Where v the discs of the transmitter and of the receiver are not to operate upon the same power supply, then it is apparent that the ileld synchronizing signal may be causedto control, in known' manner, the operation of the driving motor of the receiver, so that synchronous operation is readily maintained.

In the arrangement hereinabove discussed, for instance, the reversing switch units h15, 11 and 19 have been diagrammatically illustrated as comprising a plurality of tubes with a switch element arranged to include both tubes in circuit, or to by-pass one tube, depending upon the desired polarity of output signal from the unit. It is, of course, apparent that this is one of many suitable forms of control units for the purpose. Other forms may be used without departing from -the spirit and scope of what is herein disclosed,

and consequently the diagrammatic illustration is to be regarded as purely illustrative.

Among the other forms of arrangements which may be used as the reversing switch arrangement, are, for instance, a single output tube whereby the output at the plate or anode may be used for one polarity of signal, and the output at' the cathode may be used for another polarity of signal. A tube oi' this form may be used merely by altering the position of the control switch, such for instance as the switch schematically represented by-Fig. 3. Likewise, various forms of volume control units may be provided in place of the potentiometer controls schematically represented as connected to the output of the various reversing switch units.

Further, it is to be understood that any representations of the mixer amplifiers and the delay circuits are purely and entirely schematic, since such instrumentalities are well known in the art and therefore the illustration is not -in any way to be considered as limiting, but rather as purely illustrative.

In the arrangement of Fig. 4, a further modication of the invention has been provided. This may briefly be described as constituting a form wherein the channel width to transmit the color image representation may be regarded as having been increased over that disclosed by Fig. 3, in that provision is made for separate 'channels to transmit'simultaneously the image representations corresponding to the red, the green and the lblue component color images, and, after a plurality of such image iields representing such colors have been transmitted, a key image ileld corresponding to an orthochromatic image may be simultaneously transmitted over all of the several channels.

In the arrangement of Fig. 4 as it is diagrammatically represented by the schematic illustration, the light of the image (not shown) is adapted to be directed along the optical path |3| and through the optical system |33. and thence, by

means of a plurality of half-silvered mirrors |35 and |31, a portion of the light is permitted to pass directly along the initial opticalpath I 3| or in a direction at right angles thereto. 4The half-silvered mirror |35 thus permits the orthof chromatic image rays `|3| to split into two paths,

of which the light reilected from the mirror surface |35 is directed along a path |35 into an image scanning tube |39 through an appropriate illter 4| which is adapted to direct upon the mosaic electrode |43 of the image scanning or camera tube |39 a light image of red characteristics, for instance. The unreilected rays which pass through the half-silvered mirror |35 are then directed along the path |45 to impinge upon the second half-silvered mirror |31, from which ra portion of the rays is directed along a path |41 and another portion of the rays is passed directly through the half-silvered mirror surface |31 along a path |49.

It will be assumed, for instance, that the reilected rays traveling along the light path |41 impinge upon the mosaic electrode |5| of the camera or image scanning tube |53 after passing through a lter |55 which is adapted to direct rays corresponding to the green image upon the mosaic electrode of the camera or image scanning tube |53. Likewise, the light rays passing along the light path |49 are adapted to enter the image scanning or camera tube |51 and to fall upon the mosaic electrode |59 thereof after havorthochromatic image directed along the light path |49. Thus, a light image is simultaneously impressed upon allot the image scanning or camera tubes |39, |53 and |51, but the light image upon tube |39 is that corresponding to the red image; the light image upon the tube |53 is that 'corresponding to the green image, and the light image upon the tube |51 is that corresponding to the blue image, assuming the selection of filters as hereinabove outlined.

Since light losses occur in the half-silvered mirrors |35 and |31, the density oi.' the illters |4| and |55 is such' as to compensate for the loss and make the general intensity of the optical image impinging upon the mosaic electrodes |43 and of tubes |39 and |53 respectively substantially of the same order as that of the image cast upon the mosaic |59 of the camera or image scanning tube |51. In this manner, equalization of the outputs is reasonably well maintained.

'nie tubes |31, |53 and |51 have been illustrated in a most schematic form, but it is to be understood that the tubes are generally of the type illustrated in Fig. 3 by the image scanning tube 21, so that when the mosaic electrodes |43, 5| and |59 of all of these tubes are scanned by the usual cathode ray scanning beam, output signals will result which appear in the youtput conr ductors |5I, |52 and |53 connected respectively to the collecting electrode of the mosaics. Accordingly, these output video signals are appropriately amplified in the ampliiiers |54, |55 and |55, from which output energy is supplied to the several commutators |51, |58 and |59 by way of the commutator brushes |10, |1| and |12 connected respectively to the conductors |13, |14 and |15. I'he signal outputs in th'ese respective conductors are those representative oi' the simultaneously scanned red, green and blue images.

The various commutator elements |51. |58 and |59 are appropriately driven from a suitable prime mover (not shown), so that they revolve in synchronism and co-phaseally.

Since it was assumed, from what was hereinabove stated, that the transmission of the signals representing the scanned images would take place in such a manner that three image iields representing diierent color images would be transmitted simultaneously and in a sequence of three to be followed by a single transmission of an orthochromatic image on all transmission channels, the commutators |51, |58 and |59 are provided with commutating segments |15 and |11 each respectively, which extend for substantially 270 of the periphery and 90 of the periphery with suitable insulating segments |18 and |18' separating each section of the commutator. The longer segment |15 of the commutator is connected to a second commutator ring |19 for each commutator, from which, by means of the brushes |80, |8| and |82, the respective red, green and blue image signals are derived to be fed to the separate transmitter arnpliiiers |84, |85 and |85 connected respectively thereto by way of the conductors |81, |88 and |89. Th'e rings I 19 have insulating segments (as shown) to correspond in position to the insulating from which energy is picked up by means of a se ries of brushes |93, |94 and |95 and then fed by way of the conductor |95 connected to all orf the brushes |93, |94 and |95 to energize simultaneously all of the transmitter ampliflers |84, |85 and |85.

It accordingly is apparent that the transmitter amplifiers |84, las and |85 are seprately 4 tality.

l2 energized with the red, the green and the blue video signal components, respectively, during three-quarters of any unit time period corresponding. for instance, to the time to scan four picture fields. During the remaining one-quarter of the assumed unit time period. the various transmitter amplifiers are energized by the combined output of all of the camera or image scanning tubes |39, |53 and |51 as derived from the amplifiers |54, |55 and |55, so that thesignal energy appearing on the conductor |95, for instance, is that corresponding to an orthochromatic image, and thus, over each channel corresponding to the various colors` chosen, there will be transmitted signals both of individual color and of the combined color representing the three selected components. The output from the various transmitter ampliilers |84, |85 and |85 is then ted by way of conductors |91, |98 and |99, for instance, to any suitable form of transmission channel, such as a radio link or a wire line transmission link, orv toa suitable monitor instrumen- It has not been shown by the diagrammatic representation olf Fig. 4, but is to be understood that scanning beams in all of the tubes |39, |53 and |51 for scanning the respective mosaic electrodes thereof are to operate simultaneously so as to strike the various mosaic elements in substantially identical spacial relationships. Each scanned raster is to be homologous and equidimensional. To this end, it is preferable to provide a single source of beam deilecting energy to be applied to deflect the cathode ray beams, in order that synchronous and co-phaseal relationship shall be maintained between each. It is, of course, to be understood that to achieve this objective it is desirable that the geometry of the scanning tubes substantially coincides, and that the applied operating voltages' to each tube likewise substantially correspond in order that the general operating parameters for all the scanning tubes shall -be alike. This, however, forms no specific part of the present invention except insofar as it co-operates with the remaining elements to produce the complete system. The arrangement vfor obtaining controlled movements of the scanning beams will be discussed more particularly in a companion application, Ser. No. 548,238, which was flied Aug. 5, 1944.

It is to be appreciated, in the arrangement illustrated by Fig. 4. that what is herein termed an orthochromatic or key image is merely one of several forms which might be used and represents one acceptable form. Other forms of key images may be derived from signal output of separate image pickup or camera tubes receiving the light image from any of the optical paths |3I, |31, |45 and |49 prio'r to the time when the light of the images has passed through' any lter. The key image signals thus derived may, as heretofore stated, correspond to the visual luminosity response, or to ultra-violet, or infra-red versions of the image which is picked up, or to any other selected form of key image signal. In any of these cases, such key image signal will be used identically in the manner hereinbefore set forth, that is, such key image signals will be impressed upon the conductor and th'us caused to energize all of transmitter ampliers and channels during the period corresponding to the passage of such segments as |11 under the corresponding contact brush.

,It is thus apparent, from what has been pointed out, that the system of Fig. 4 is a modiiication which provides for simultaneously transmit- Accordingly, the method last described is cyclic, t,

insofar as the succession of the red, the green and the'blue and the key images is concerned, but it is simultaneous so far as the production of the key image by the concurrent transmission and reception of thered, the green and the blue equalf Y, ized brightness images is concerned.

3 may be termed, a combined simultaneous and n.

cyclic method,since it is a simultaneous method for the separate color transmissions but cyclic between the color images and the key image.

For receiving the images transmitted by the arrangement of Fig. 4, various arrangements may be provided which would consist, for instance, of. a single electron tube having a laminated luminescent target which would respond to reproduce the various picture colors, and in which the laminations would be so located that independent electron guns Within th'e receiving cathode ray tube might operate to direct scanning beams thereagainst, or, alternatively, the system may be of the type disclosed by my applications, Ser. Nos. 548,238 and 548,239, each led Aug. 5, 1944, and each relating to color television. Further, as known in the art, the receiving instrumentality may comprise a plurality of separate cathode ray image reproducing tubes individually having target areas adapted to reproduce the red, the green and the blue images and arranged to direct'l the issuing light simultaneously upon a single viewing target area at which the light, image c-f all tubes is superimposed.

In a further alternative form, the receiver instrumentality, which is not herein specifically illustrated since it does not form a, specific part of the invention except insofar as it is necessary to a complete understanding of the invention, will be assumed to comprise a plurality of separate cathode ray image reproducing tubes each being adapted to reproduce a. pure black and white image and having a. lter disc coordinated with each, with the lter disc ofthe respective channels being formed according to the arrangement of Fig. 2, except that for one channel all of the areas I3, I5 and l1 would, for instance, be adapted to produce a. red image, whereas for the second channel, all of these areas would be adapted to produce a green image, and for the third channel, these areas would be adapted to produce a blue image. a

Synchronization between the scannings of the receiver and the transmitter for the system last described is, of course, to be maintained in known ways; such, for instance, that described in connection with the description of Fig. 3, and there- Y fore has not been herein illustrated in detail.

In a further modication of the invention, not herein illustrated, provision may be made for both simultaneous and cyclic transmission of the image elds, in that the red image may i'lrst be transmitted for one eld, the green image then may be transmitted to follow for a second iield, and the blue image caused to follow for the third eld, after which these three image fields are simultaneously transmitted in equalized brightness to provide a corresponding key image or orthochromatic reproduction, and thus the reproduction of the images at the receiver is a cyclic series of red, green and blue images, for instance, followed by a key image.

In still a further form, the red image, the green image and the blue image may be simultaneously transmitted and received to produce the color image, and then the equalized red, green and blue images, corresponding to the key image, may be cyclically transmitted so' that their reception, in succession, will produce the necessary key images. Such a method, not herein illustrated, is simultaneous sc far as the tricolor image is concerned, but cyclic so far as the key image is concerned.

Further, in connection with the arrangement herein described in connection with Fig. 4, it is apparent that if the ychoice of time duration for ,transmitting the color images, such as those rep- It will be appreciated that while mechanical commutation has generally been illustrated in y Figs. 3 and 4 as representative of the principles of the invention and for the purpose of indicating the switching operations, an al1-electric switching method'may readily be utilized. Such circuits are well known in the art as illustrated, for instance, by patents heretofore'granted to C.- C. Shumard, No. 2,146,862, and C. S. Roys and H. F. Mayer, No. 2,089,430, as well as the application of Whitaker, Serial No. 436,983, filed March 31, 1942, for an invention entitled Electrical circuits.

It will also be readily apparent to those skilled in the art that the application of the key image to simultaneous color television transmission systems usually makes the delay networks unnecessary and requires an additional transmitting tube with an appropriate optical system and lter at the transmitter and an additional receiver tube without a filter and with an appropriate optical system to combine the black and white key imwhich compr'mes the steps of producing groups of signals representative of .predetermined additive primary colors of the object whose image isto be reproduced, producing a series of signals proportionate to the luminous emission of the colors y of the object, and energizing a transmission chanthe object whose image is to be reproduced, producing a further independent series of signals representative only of the visual brightness of the colors of the object, and sequentially transmitting all of the produced series of signals.

the last independent series ofsignals is repre- Y sentative of the intrinsic brightness of the colors of the object. and transmitting all of the produced series oi' signals in sequence.

4. 'I'he method of color television. transmission which comprises the steps of` producing groups of signals representative of predetermined primarycolors of'the object whose image is to be reproduced, producing a series o1' signals representative only of the intrinsic brightness of the colors of the object, and cyclically energizing a transmission channel by all of the produced series of signals.

5. The method of color vtelevision transmission which comprises the steps oi' producing independent series of signals each representative of 'one of a predetermined plurality of additive primary colors of the object whose image is to be reproduced, producing a further series of signals representative of a key image of a brightness proportionate to the luminous emission of the object whose image is to be reproduced, and supplying all of the produced series of signals to a communication channel.

6. The method o! color television transmission which comprises the steps of producing independent series of signals each representative of one of a predetermined plurality of additive primary colors of the object whose image is to be reproduced, producing a further series oi' signals representative o! a key image of the object whose image is to be reproduced, controlling the signal level of the independent series of signals by the key image signals, and then transmitting all of the produced series of signals in sequence.

'1. The method of color television transmission which comprises the steps of producing groups of signals representative of a .plurality of predeter.

mined additive primary colors of the object whose image is to be reproduced, producing a series o1' signals representative only of the intrinsic brightness of the colors of the object, controlling the signal level of the signals representing primary colors under the influence of the signals representing intrinsic brightness, and cyclically transmitting 'all of the produced series of signals.

8. The method of color television transmission which comprises the steps of producing a plurality of independent series of signals individually representative of predetermined selected additive primary colors of the object whose image is to be reproduced, producing a further independent series of signals representative only ol.' the intrinsic brightness of the colors of the object, substantially uniformly controlling the signal level of the plurality of series of signals under the iniiuence of the last named series of signals, and then transmitting all of the produced series oi 9. The method of color television transmission which comprises the steps of producing a plu- 10. The method o!v reproducing color television images which comprises the steps of receiving a series of signals representative of a plurality of predetermined additive primary colors, each series corresponding tothe object whose image is to be reproduced, receiving a series of signals representative of a key image, additively colored images from the received signals representative of the separate primary color images, producing a black and white image from the signals representative of the key image, and combining all of the produced images.

11. The method of transmitting and receiving color television images which comprises the steps of producing a, plurality of series oi' signals each representative oi' one of a predetermined plurality of additive primary colors of the object whose image is to be reproduced, yproducing a series of signals representative only of the intrinsic brightness of the colors of the object, transmitting all of the produced series of signals, receiving all of the transmitted signals, producing color images corresponding to the signals of the primary co1- ors, producing a black and white image corresponding to the signals representative of the intrinsic brightness of the object, and addtively combining all of the produced images.

12. A method of color television comprising producing a plurality of independent series of signals representing in sequence a predetermined plurality of primary colors of an image, producing 'after a predetermined number of series ci' signals representative of primary colors an independent series of signals representative of the intrinsic brilliance of all colors of the image, independently amplifying the signals of eachv of the series produced, controlling the sequence of ampliiication to coincide with the production of the individual series of signals, deriving a control series of signals by delaying the signals representative of the brightness of the image for periods which are multiples of the scanning iield period for controlling the ampliiication level of each of the independent series of signals, and then combining all of the produced series of signals for transmission sequentially.'

13. A system of'color television which comprises scanning means for producing a plurality oi' independent series of signals each representative of one oi' a plurality of predetermined primary colors of an object whose image is to be reproduced, means to produce an independent series of signals representative of a key image of the object whose image `is to be reproduced, and distributor means for cyclically transmitting all of image oi' the object so as to produce from the rality of series of signals each representative of scanning means an independent series of signals representative of a key image of the object whose image is to be reproduced, and distributor means for cyclically transmitting all of the produced series of signals.

15. A system oi.' color television winch comprises scanning means for sequentially producing independent series of signals individually representa.- tive of diil'erent ones of selected primarycolors of an object whose image is to be reproduced,

co-operating filter means for analyzing an opticalimage to produce a plurality of independent series of signals representing in sequence predetermined primary colors of the image, means to produce from the scanning device, following a predetermined number of series of signals representative of primary colors, an independent series of signals representative `of the intrinsic brilliance of all colors of the image, and means for combining all of the produced series of signals for energizing a transmission line sequentially by the independent 'series of produced signal energy.

17. In a color television system, a camera tube, an optical filter for revealing light of different primary colors sequentially to the tube, said camera tube providing a means for analyzing an optical image to produce a plurality of independent series of signals representing in sequence predetermined primary colors of the image, means to produce from the camera tube, following a. predetermined number of series of signals representative of primary colors, an independent series of signals representative of the intrinsic brilliance` of all colors of the image, and means for combining all of the produced series of signals for energizing a transmission line sequentially by the independent series of produced signal energy.

18. In a color television system; an image scanning tube, fllter means for revealing to said tube in sequential manner light oi' a plurality of primary color images and an orthochromatic key image, means for analyzing the light images revealed to the tube to produce a plurality of independent series of signals representing in sequence the several. primary color and key light images, independent amplifier means for amplifying the signals of each of the produced series, distributor means for controlling in sequence the energization of one only of the several amplifiers,l and means for combining all of the produced series of signals for energizing a transmission line sequentially by the independent series of produced signal energy.

19. In a color television system a camera tube and co-operating filter means for analyzing an optical image to produce a plurality of independent series of signals representing in sequence predetermined primary colors of the image, means to produce from the camera tube, following a predetermined number of series of signals representative of primary colors, an independent series of signals representative of the intrinsic brilliance of all colors of the image, independent amplifier means for amplifying the signals of each of the series produced, distributor means for controlling in sequence the energization of each of the several amplifiers, and means for combining all of the produced series of signals for energizing a transmission line sequentially by the independent series of produced signal energy.

20. In a color television system, a camera tube and co-operating iilter means for analyzing an optical image to produce a plurality of independent series of signals representing, in sequence,

a predetermined selected number of primary color versions of the optical image, means to produce from the camera tube, following a. predetermined number of series of signals representative of primary colors, an independent key series of signals` representative of the intrinsic brilliance of all colors of the image, independent amplifier means for amplifying\the signals of each of the series produced, distributor means for controlling, in sequence, the energization of the several ampliners so that one only is instantaneously energized, a plurality of delay circuits, means to energize the delay circuits by the signals representative of the brightness of the image, means for controlling the amplification level of the amplifiers for each of the independent series from the delay circuit, and means for combining all of the produced series ofsignals for energizing a transmission line sequentially by the independent series of produced signal energy.

2l. In a color television system, an image scanning tube, iilter means for revealing to said tube in sequential manner light of a plurality of primary color images and an orthochromatic key image, means for analyzing the light images revealed tothe tube to produce a plurality of independent `series of signals representing in sequence the several primary color and key light images, independent amplifier means for amplifying the signals of each of the produced series, distributor means for controlling in sequence the energization of one only of the several amplifiers, means includinga plurality of delay circuits energized by the signals representative of the brightness of the key image for controlling the amplication level of the ampliners for each of the independent series, and means for combining all of the produced series of signals for energizing a. transmission line sequentially by the independent series of produced signal energy.

22. In a color television system, an image scanning tube, lter means for revealing to said tube in sequential manner light of a plurality of primary color images and an orthochromatic key image, means for analyzing .fthe light images revealed to the tube to produce a plurality of independent series of signals representing in sequence the several primary color and key light images, independent amplifier means for amplifying the signals of each of the produced series, distributor means for controlling in sequence the energize.- tion of one only of the several amplifiers, means for deriving from the key image a control signal for controlling in the sequence of scanning the amplification level of each of the amplifiers for amplifying each of the chosen primary colors, said means comprising a, plurality of delay circuits having individual time delay periods proportional to the time delay between the production of each controlled series of signals representing a, primary color from the time of production of the key image signals, reversing switch means for causing the polarity of the signal applied to control the amplification in the amplifier means to coincide with or oppose the polarity of the signals representing the different primary color images, and means for combining all of the produced series of signals for energizing a transmission line sequentially by the independent series of produced signal energy.

23. A color television system comprising an electronic camera tube having means for projecting an optical image thereon, filter means interposed in the path of the optical image directed upon the said camera tube for illuminating the said scanning tube in sequence by images of predetermined selected primary colors followed by a key -image representing the general over-al1 brilliance of the optical image, a plurality of signal amplifier means of a number equal to the number of primary colors and the key picture, distributor means for cyclically and sequentially energizing individual ampliilers of the plurality by one only 1 of the plurality of series of signals representing the selected primary coloreimages and the keyimage, a combining circuit for combining all of the produced images, means for deriving from the key image a control signal for controlling the amplification level of the ampliers for amplifying each of the chosen primary colors, said means comprising a plurality of delay circuits having time delays equal in sequence to integrals of the time period required to produce each of the controlled series of signals representing a primary color, reversing switch means for controlling the polarity of the signal applied to control the amplication in the amplifier means, and means for applying all of the signals to a transmission channel.

24. 'I'he method of additive color television transmission which comprises the steps of producing independent series of signals representative of selected predetermined primary colors according to which the object whose image is to be reproduced is to be analyzed, producing a further independent series of signals representative only of the combined intrinsic brightness of the spectral colors of the object, and consecutively transmitting all of the produced series of signals.

25. In an additive color television system a plurality of sources of video signals individually corresponding to selected component color images and to a. key image of an object or scene respectively, means for continuously controlling within their amplitude range each element of the component color signals in accordance with the spatially homologous portion of the key image signals, and means to energize a transmission channel by each of the resulting component color image signals and the key image signals.

26. The method of additive color television transmission which comprises the steps of producing groups of signals representative of predetermined primary colors of the object whose image is to be reproduced, producing a series of key image signals representative only of the visual brightness of the colors of the object, and energizing at least one transmission channel by all of the produced series of signals.

ALFRED N. GOLDSMITH.

REFERENCES CITED The Vfollowing references are of record in the le of this patent:

UNITED STATES PATENTS 

